We shall continue work devoted to the study of the regulation of the immune response to contact allergens. Allergic contact determatitis will be examined in chickens, mice and guinea pigs. We shall investigate the effect of limited field x-ray on the acquisition and expression of contact allergly in guinea pigs. We shall determine optimum conditions for immunopotentiation of allergic contact dermatitis by cyclophosphamide and by complete Freund's adjuvant in chickens; in some cases these chickens will have been rendered B cell depleted by chemical bursectomy. Passive transfer of suppressor cells (of allergic contact dermatitis) will be undertaken in normal and in immunodeficient mice with a view to identifying the suppressor cell class and the mechanism of action of the suppressor cell.